980 research outputs found
Quasi-Exact Solvability and the direct approach to invariant subspaces
We propose a more direct approach to constructing differential operators that
preserve polynomial subspaces than the one based on considering elements of the
enveloping algebra of sl(2). This approach is used here to construct new
exactly solvable and quasi-exactly solvable quantum Hamiltonians on the line
which are not Lie-algebraic. It is also applied to generate potentials with
multiple algebraic sectors. We discuss two illustrative examples of these two
applications: an interesting generalization of the Lam\'e potential which
posses four algebraic sectors, and a quasi-exactly solvable deformation of the
Morse potential which is not Lie-algebraic.Comment: 17 pages, 3 figure
Boundary conditions for hyperbolic formulations of the Einstein equations
In regards to the initial-boundary value problem of the Einstein equations,
we argue that the projection of the Einstein equations along the normal to the
boundary yields necessary and appropriate boundary conditions for a wide class
of equivalent formulations. We explicitly show that this is so for the
Einstein-Christoffel formulation of the Einstein equations in the case of
spherical symmetry.Comment: 15 pages; text added and typesetting errors corrected; to appear in
Classical and Quantum Gravit
An Update on EMU Sovereign Yield Spread Drivers in Times of Crisis: A Panel Data Analysis
Suppression of Tc in the (Y0.9Ca0.1)Ba2Cu4-xFexO8 system
In this paper, the effects produced by the iron substitutions in the
(Y0.9Ca0.1)Ba2Cu4-xFexO8 system on the superconducting and structural
properties are studied. The Rietveld fit of the crystal structure and Mossbauer
spectroscopy results of (Y0.9Ca0.1)Ba2Cu4-xFexO8 samples indicate that, the
iron atoms occupy the Cu(1) sites of the (Cu-O)2 double chain in fivefold
coordination at low iron concentrations. Besides at high iron concentrations
the iron atoms occupy the Cu(1) sites of single Cu-O chainss and Cu(2) sites in
the CuO2 planes of the (Y0.9Ca0.1)Ba2Cu4-xFexO8 phase with structural defects.
Simultaneouly, as iron concentration increases, a faster decrease of Tc is
observed in this material comapred with the YBa2Cu3-xFexO7-y system. According
to the charge transfer model proposed for YBa2Cu4O8 under pressure, the
decrease in the Cu(1)-O(4) bond length in parallel to the increase in the
Cu(2)-O(4) bond length may affect the charge transfer mechanism leading to the
suppression of Tc.Comment: submitted to Journal of Physics: Condensed Matter on 12 October 2001,
8 figures, 2 tables, 9 page
Sex and Heart Failure Treatment Prescription and Adherence
Heart disease is the leading cause of death in both men and women in developed countries. Heart failure (HF) contributes to significant morbidity and mortality and continues to remain on the rise. While advances in pharmacological therapies have improved its prognosis, there remain a number of unanswered questions regarding the impact of these therapies in women. Current HF guidelines recommend up-titration of neurohormonal blockade, to the same target doses in both men and women but several factors may impair achieving this goal in women: more adverse drug reactions, reduced adherence and even lack of evidence on the optimal drug dose. Systematic under-representation of women in cardiovascular drug trials hinders the identification of sex differences in the efficacy and safety of cardiovascular medications. Women are also under-represented in device therapy trials and are 30% less likely to receive a device in clinical practice. Despite presenting with fewer ventricular arrythmias and having an increased risk of implant complications, women show better response to resynchronization therapy, with lower mortality and HF hospitalizations. Fewer women receive advanced HF therapies. They have a better post-heart transplant survival compared to men, but an increased immunological risk needs to be acknowledged. Technological advances in mechanical circulatory support, with smaller and more hemocompatible devices, will likely increase their implantation in women. This review outlines current evidence regarding sex-related differences in prescription, adherence, adverse events, and prognostic impact of the main management strategies for HF
Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football
IMPORTANCE: Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE).
OBJECTIVE: To determine the neuropathological and clinical features of deceased football players with CTE.
DESIGN, SETTING, AND PARTICIPANTS: Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history.
EXPOSURES: Participation in American football at any level of play.
MAIN OUTCOMES AND MEASURES: Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia.
RESULTS: Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia.
CONCLUSIONS AND RELEVANCE: In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.This study received support from NINDS (grants U01 NS086659, R01 NS078337, R56 NS078337, U01 NS093334, and F32 NS096803), the National Institute on Aging (grants K23 AG046377, P30AG13846 and supplement 0572063345-5, R01 AG1649), the US Department of Defense (grant W81XWH-13-2-0064), the US Department of Veterans Affairs (I01 CX001038), the Veterans Affairs Biorepository (CSP 501), the Veterans Affairs Rehabilitation Research and Development Traumatic Brain Injury Center of Excellence (grant B6796-C), the Department of Defense Peer Reviewed Alzheimer’s Research Program (grant 13267017), the National Operating Committee on Standards for Athletic Equipment, the Alzheimer’s Association (grants NIRG-15-362697 and NIRG-305779), the Concussion Legacy Foundation, the Andlinger Family Foundation, the WWE, and the NFL
Association of Rare Coding Mutations With Alzheimer Disease and Other Dementias Among Adults of European Ancestry
MPORTANCE Some of the unexplained heritability of Alzheimer disease (AD) may be due to rare
variants whose effects are not captured in genome-wide association studies because very large
samples are needed to observe statistically significant associations.
OBJECTIVE To identify genetic variants associated with AD risk using a nonstatistical approach.
DESIGN, SETTING, AND PARTICIPANTS Genetic association study in which rare variants were
identified by whole-exome sequencing in unrelated individuals of European ancestry from the
Alzheimer’s Disease Sequencing Project (ADSP). Data were analyzed between March 2017 and
September 2018.
MAIN OUTCOMES AND MEASURES Minor alleles genome-wide and in 95 genes previously
associated with AD, AD-related traits, or other dementias were tabulated and filtered for predicted
functional impact and occurrence in participants with AD but not controls. Support for several
findings was sought in a whole-exome sequencing data set comprising 19 affected relative pairs from
Utah high-risk pedigrees and whole-genome sequencing data sets from the ADSP and Alzheimer’s
Disease Neuroimaging Initiative.
RESULTS Among 5617 participants with AD (3202 [57.0%] women; mean [SD] age, 76.4 [9.3] years)
and 4594 controls (2719 [59.0%] women; mean [SD] age, 86.5 [4.5] years), a total of 24 variants
with moderate or high functional impact from 19 genes were observed in 10 or more participants
with AD but not in controls. These variants included a missense mutation (rs149307620 [p.A284T],
n = 10) in NOTCH3, a gene in which coding mutations are associated with cerebral autosomaldominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), that was also
identified in 1 participant with AD and 1 participant with mild cognitive impairment in the whole
genome sequencing data sets. Four participants with AD carried the TREM2 rs104894002 (p.Q33X)
high-impact mutation that, in homozygous form, causes Nasu-Hakola disease, a rare disorder
characterized by early-onset dementia and multifocal bone cysts, suggesting an intermediate
inheritance model for the mutation. Compared with controls, participants with AD had a significantly
higher burden of deleterious rare coding variants in dementia-associated genes (2314 vs 3354
cumulative variants, respectively; P = .006).
CONCLUSIONS AND RELEVANCE Different mutations in the same gene or variable dose of a
mutation may be associated with result in distinct dementias. These findings suggest that minor
differences in the structure or amount of protein may be associated with in different clinical outcomes. Understanding these genotype-phenotype associations may provide further insight into
the pathogenic nature of the mutations, as well as offer clues for developing new therapeutic targets
An?lisis de los elementos cr?ticos para el desarrollo de proveedores en empresas de la gran miner?a en el Per?
En esta investigaci?n se describen las caracter?sticas de los elementos cr?ticos para el desarrollo de proveedores en empresas de la gran miner?a en el Per?. Como parte de la gesti?n de las relaciones con proveedores, las empresas realizan desarrollo de proveedores cuando participan activamente en esfuerzos para mejorar el desempe?o y capacidades de sus proveedores. Sobre la base del marco de referencia para el desarrollo de proveedores de Sucky y Durst (2013), se definen las variables que describen las condiciones influyentes, factores de ?xito, estrategias e impactos del desarrollo de proveedores en una muestra de seis empresas representativas de la gran miner?a peruana. Para ello se realizan entrevistas semiestructuradas a ejecutivos de log?stica, compras y contratos, as? como revisiones de reportes de sostenibilidad y otros documentos. El estudio concluye que la estrategia de las empresas es desarrollar las capacidades de sus proveedores locales, con el objetivo de mantener una buena relaci?n con las comunidades de sus ?reas de influencia directa. La baja capacidad del proveedor local representa la principal condici?n influyente, y la actitud estrat?gica hacia el proveedor es el principal factor de ?xito. Finalmente, el desarrollo de proveedores tiene impactos positivos en las empresas y en sus proveedores locales
Caffeine, a Risk Factor for Osteoarthritis and Longitudinal Bone Growth Inhibition
Osteoarthritis (OA), the most common chronic rheumatic disease, is mainly characterized by a progressive degradation of the hyaline articular cartilage, which is essential for correct joint function, lubrication, and resistance. Articular cartilage disturbances lead to joint failure, pain, and disability. Hyaline cartilage is also present in the growth plate and plays a key role in longitudinal bone growth. Alterations of this cartilage by diverse pathologies have been related to longitudinal bone growth inhibition (LBGI), which leads to growth retardation. Diet can play a crucial role in processes involved in the OA and LBGI's onset and evolution. Specifically, there is ample evidence pointing to the negative impacts of caffeine consumption on hyaline cartilage. However, its effects on these tissues have not been reviewed. Accordingly, in this review, we summarize all current knowledge in the PubMed database about caffeine catabolic effects on articular and growth plate cartilage. Specifically, we focus on the correlation between OA and LBGI with caffeine prenatal or direct exposure. Overall, there is ample evidence indicating that caffeine intake negatively affects the physiology of both articular and growth plate cartilage, increasing consumers predisposition to suffer OA and LBGI. As a result, caffeine consumption should be avoided for these pathologies
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